Looking at simple motor dot com and have some questions regardin making electric motor from scratch

[headhunter]

We'll I'm going to try making an electric motor from scratch and have been researching it on the internet.  I want to make a motor using one of my .5"X.5"X2" neos inside of a plastic molded cyclinder on bearings with 2 coils running it.  I want to make this brushless but haven't figured out on how to alternate the current to the 2 coils.

This is what I've figured so far.  Have the coils hooked together and as the magnets N approaches once coil, it adds electricity to the coils,(one coil one way the other the opposite) so it would send + through one side of the wire and - the other.  

But how would I have it switch the + and - as the N approaches the second coil?

Ivan.

[tinker]

Good starter site:

http://www.simplemotor.com/rsmotor.htm

[thunderhead]

If you apply three sine wave voltages to most of the generator designs that are described on this board, they will act as motors.  They will spin at the speed of oscillation of the sine waves.  This is a brushless permanemt magnet motor.

If you want your motor to run at just one speed, this is probably all you need.  If you want variable speeds, you will need some way to vary the current in the coils according to the position of the magnets.  The most reliable way to do this is with an optical or Hall effect position sensor.  But to get that going, especially if you want your motor to do a significant amount of work, will require a fair amount of electronics knowledge and experimentation.

What is your application?

[headhunter]

Well I just wanted to make a brushless electric motor as an experiment.  The web page posted by tinker is interesting as it might do what I want it to do... but the fact that the switch might fuse if too much amps/volts go through it doesn't sounds so hot.

Is there some sort of relay or switch that has 2 wires in and 2 out and can cross them back and forth as stated by a 5th and/or 6th wire into the unit?  Any sort of solid state devices that can do this?

The hall effect might work, will have too look more into the optical.

Ivan.

[headhunter]

Here's another idea, say I use an optical sensor or a halleffect sensor.  Could I have them trigger a set of transistors in order to flip the + and - in the coils then?  Would require a little setting up but might work.  What kind of transistors(names would be good and possibily price too) would be required for a 12v 1-10amp setup for this?

Ivan.

[thunderhead]

The reason they've used a reed relay is because it's easy to understand, and easy for the home constructor to construct.  Transistors get more complicated, and when they break it's less obvious (if they don't let any magic smoke out).

A reed relay motor will never go very fast or deliver much power, since it is limited by the changeover time for the relay and by the maximum current of the contacts.  You can get a relay that controls two changeover switches with a single contact - it's called a "double pole changeover relay" or a "double pole double throw relay".  Since engineers are fond of TLA's and ETLA's, you may see it called a DPDT relay.  

Have fun. :-)